Transverse sliding breech bolt lock



April 29, 1952 D. v. scHNEPEL 2,594,354

TRANSVERSE SLIDING BREECH BOLT LOCK Filed Dec. 11, 1945 3 Sheets-Shea?l l Il qualms AV1 E :11n-

y mywwmm April 29,-1952- D. v. scHNEPEL TRANSVERSE SLIDING BREECH BOLT LOCK `3 sheets-sheet 2 ljiledfuec. 1v1. 1945 llllll lllldllll I|| Illl Il f EN LII pri 29, 1952 D. v. scHNEPEL 2,594,354

TRANSVERSE SLIDINGBREECH BOLT LOCK Filedlnec. 11, 1945 s snags-sheet :s

131371151115 V'- Suhl-Lapel Patented pr. 29, 1952 UNITED STATES PA'lTzNT OFFICE TRANSVERSE SLIDING BREECH BOLT LOCK s Douglas V. Schnepel, Elmira-N. Y. v I 'v Application Decemberl 11, 1945,'SerialNo. 634,326

` Y 2 claims. (Cisa-187) (Granted under the act 'of March 3, 1883, as

The invention described herein may be manuf factured and used by or for the Governmentl for permitting safe opening of the breech block.

Still another object of this invention is to provide an automatic firearm having a firing pin member arranged to be moved longitudinally by gas actuated means to effect unlocking of the breech block of the firearm.

Another object of this invention is to provide an improved belt feed lever which is mounted on the breech block of such firearm and actuated by cam means to advance the cartridge belt into` the receiver of the firearm.

The specic nature ofthe invention as well as other objects and advantages thereof will clearlyv appear from a description of a preferred vembodiment as shown in the accompanying drawings in which:

Fig. 1 is a partial longitudinal cross-sectional view of the assembled firearm.

Fig. 2 is a V-partial top elevational View of the rearm. l

Fig. '3 is an enlarged top elevational view of the operating rod and driving spring housing.

Fig; 4 is a perspective view of the cam bar lock actuating cam.

Fig. 5 is an enlarged sectional view of the gas regulator.

Fig. 6His an enlarged isometric view of the breech block.

Fig. 'lv is an enlarged bottom elevational view ofthe cam bar lock.

Fig. 8 is' an enlarged front elevational view of the breech block lock;

Fig. 9 is an enlarged top elevational view of Fig. 10 is an enlarged perspective view of the extractor.

Fig. 11 is an enlarged detail view of the T-slot Y provided in theforward end of the breech block.

l amended April 30, 1928;'370A OL G. 757) 2 i f line I3-'I3 of Fig. 3. Fig. 14 is a view 'of Fig. 12 taken from the front.

. The firearm shown in Fig. 1 comprises essentially a receiver. I, a breech block or bolt 2, and

a barrel3. Breech block 2 is mounted within receiver I Vfor reciprocating movement therein Yand such breech block is actuated by an operating rod 4 in a manner to be presently described.

.Receiver I is preferably channel shaped with the open' side thereof at the top as shown in Figs. 1 and 2. A trunnion 5 is secured Vwithin the forward end of receiver I'preferably by rivets. Y A

downwardly projecting lug 6 is provided on trunnion 5 and a transverse hole 'I is provided in lug 6. The hole 'I permits convenient mounting ofthe forward end of receiver I on a tripod (not shown) An upstanding lug 8 is provided on top of trunnion 5 and a rearwardly projecting cover 9 is pivotally secured thereto by a hinge joint Ill as shown in Fig. 1. Cover 9 will be described in more detail later.

A back plate I I is welded or` otherwise secured to receiver I in the rear thereof as shown in Fig. 1. A conventional buifer mechanism I2, preferably such as is used on the caliber .30 Browning machine gun, model of 191'7`, is horizontally mounted on the rear of back plate II,`preferably verse pin I6.

- videdon the forward end of trigger I5 which engages breech block 2 in a manner to be later described. A spring I8 inserted in a vertical hole fll in back plate II bears against the topl of trigger I5 to bias the front end of trigger I5 upwardly so thatthe lug I1 will contact the bottom of breech block 2 when the pressure of the finger y thereof as shown in Fig. 1.

is removed from trigger I5.V

"A downwardly projecting bracket 2li is secured to the bottom of vreceiver `I l at the rear A transverse-holen provided in` such bracket permits the rear end of l receiver I to be mounted on a tripod' (not shown) A longitudinal horizontal h ole 22is provided in the center of trunnion 5; The rear end-of such hole is threaded as shown at 23 .while the forward end of hole 22 is counterbored and threaded as shown at 24. Barrel 3 is inserted in `hole 22 and the threaded end thereof engages threads 23 as shown in Fig. 1 A perforated barrel jacket surrounds barrel 3 and is screwed into the counterbored threaded hole 24 provided on the forward end of trunnion 5. Barrel jacket 25 is preferably of comparatively short length and a gas cylinder bracket 26 surrounds the forward end thereof and is secured thereon preferably by a press-fit. A rearwardly extending gas tube 21 (Fig. 2) is secured within a horizontal hole 28 in bracket 26. Such hole is transversely offset relative to the barrel. Tube 21 communicates with a gas cylinder 94 to be described. Gas passage hole 28 communicates with a transverse threaded hole 29 in bracket 26. Hole 29 in turn communicates with a gas port 39 in barrel 3.

A gas regulator 3| is screwed into threaded hole 29. Regulator 3| comprises a bolt-like member. An axial recess 32 is provided in one end of regulator 3| as shown in Fig. 5. A plurality of radially disposed holes 33 communicate with recess 32. Each of the holes 33 is of varying size to permit a greater or lesser amount of gas to pass from gas port through regulator 3| into gas tube '21 to actuate the breech mechanism as Y will be later described. Holes 33 are, of course, so located on gas regulator 3| that each will selectively come opposite gas tube 21. A suitable detent (not shown) may be provided to yieldingly retain gas regulator 3| in any one of its plurality of radial positions in order that each of the holes 33 may be selectively held in alignment with gas tube 21.

Breech block 2 is a substantially rectangular member. A vertical hole 34 is provided therein centrally disposed and somewhat to the rear of the breech block. A cylindrical breech block lock 35 is inserted in hole 34. Such lock will be subsequently described. A vertically disposed T-slot 18 is provided on the front face of breech block 2 which engages the rim of a cartridge 46 to insert such cartridge into a chamber 41 in barrel 3 and to-extract the fired case as will be later described. A generally rectangular hole 36 is provided in breech block 2 extending forwardly from the rear end of the breech block along the horizontal axis of breech block 2. Such hole however does not extend through the forward end of breech block 2. A substantially rectangular slot 31 having arcuate ends is provided on the side of breech block 2 as shown in Fig. 6 and communicates with rectangular hole 36. A longitudinal slot 38 is provided on the top of breech block 2 and likewise communicates with rectangular hole 36. A firing pin hole 83 is provided in the forward end of breech block 2 having suitable configuration to receive a ring pin 61 to be described to permit such firing pin to protrude through the forward end of breech block 2 to ignite the cartridge 46 contained in chamber 41 of barrel 3 of the firearm.

An extractor 39 is pivotally mounted in slot 38 by a transverse pin 40. Extractor 39 essentially comprises a bifurcated front end portion 42 and a downwardly and rearwardly projecting rear end portion 4|. A claw 43 is pivotally mounted in the bifurcated forward end 42 of extractor 39 by a transverse pin 44. The lower end of claw 43 is of suitable configuration to engage a rim of cartridge 46. A torsion spring 48 surrounds pin 44 and claw 43 in such fashion as to bias claw 43 outwardly in order that it can readily engage the rim 45 of cartridge 46. A pin 49 projecting outwardly from the left side of extractor 39, as shown in Figs. 1 and 10, rests on top of a helical spring 59. Spring 50 is disposed within a vertical hole 5| provided in breech block 2 below pin 49. Spring 50 is provided to bias extractor 39 upwardly on the recoil stroke of breech block 2.

An extractor depressor bar 52 is pivotally mounted within bifurcated front end portion 42 of extractor 39 as shown in Figs. 1 and 10. Such bar is mounted on a transverse pin 53 and is biased upwardly by a suitable spring (not shown). Bar 52 rides on the underside of cover 9 as will be later described. A stop 19 comprising a transverse pin extends from the side of breech block '2 into longitudinal slot 38 somewhat forward of and above transverse pin 46 to limit the upward travel of extractor 39 under the .bias of spring 50.

Lock 35 as mentioned before is a cylindrical member and is vertically bifurcated as shown at |35 in Fig. 8. A transverse hole 54 is provided in lock 35 which passes through the bifurcated portion |05 of V'such lock. Two oppositely disposed upstanding integral lugs 55 are provided on top of the bifurcated end of lock 35. Where lugs 55 join lock 35 an arcuate fillet 56 is provided. Such arcuate fillet 56 engages a cam barlock 51 when breech block lock 35 is in the raised position as will be later described.

Cam bar lock 51 (Fig. '1) essentially comprises a cylindrical body member 58. In the center of such member there is provided an integral radial lug 59 and the lower end of such lug engages a cam bar 69 as will be later described. An integral radial arm 6| is provided on one end of cylindrical body member 53. An axial hole 62 is provided through body member 58 of cam bar lock 51 to pivotally mount such lock on a transverse pin 63 in the breech block 2. Pin 63 is centrally disposed with respect to the axis of hole 34 and is supported by the side walls of breech block 2. A helical spring 64 is vertically mounted in a suitable hole in lock 35 directly underneath arm 6| of cam bar lock 51. Spring 64 is provided to bias cam bar lock 51 in a counter-clockwise direction as shown in Fig. 1 in order to rotate lug 59 into engagement with cam bar 6-0 as will be presently described.

Cam bar 66 functions as the operating member for the lock 35 and comprises a narrow substantially rectangular member provided with an integral transversely projecting lug 65 on the forward end thereof. The forward end of bar 69 and lug 65 is arcuately formed as shown in Figs. 1 and 9 and the rear end of lug 65 is likewise arcuately shaped. A substantially rectangular recess 66 is provided on one side of lug 65 as shown in Fig. 9 for a purpose to be presently described. Firing pin 61 is horizontally mounted in the front end of bar 66 and is secured therein by a transverse pin 68. Slightly to the rear of the center of cam bar 69 there is provided a sloped cam slot 69. v

Cam -bar 69 is slidably mounted in rectangular hole 36 in breech block 2 for reciprocating longitudinal movement. Such mounting is effected by inserting cam bar through slot 31 into the hole 36 so that lug 65 engages in slot 31. The bifurcated end of lock 35 then surrounds cam bar 69. A transverse pin 10 inserted through a suitable transverse hole in breech block 2 passes through hole 54 in lock 35 and through cam slot 69 in cam bar 69 thereby securing lock 35 to such bar. Thus when cam bar 69 is forced rearwardly, pin 10 is forced to travel Within slot 69; hence lock 35 is raised to effect unlocking of tioned, `is hinged to the receiver on lug 8.

breech block 2. Such will be more fully described later.` Firing pin 61 is of course aligned with the axis of barrel 3 in order that it will centrally strike the primer of cartridge 46.

A scar notch 1I is provided on the underside of breech block 2 near the rear end thereof which is provided to better withstand the shock of the J locking forces.

On top of breech block 2, on the left side thereof as shown in Fig. 1, there is mounted a belt feed lever 14. Such lever 14 is a bar shaped meinber which terminates at the forwardy end in a knife-like -blade portion 11 as shown in Fig.- 12. Lever 14 is pivotally secured to breech block .'i

by a vertical bolt 15. Such bolt is screwed into a vertical threaded hole 16 provided near lthe rear end -of breech block 2. Bolt likewise passes through a suitable hole provided in the rear end of lever 14.

On the left side of breech block 2, there is provided a horizontal hole 88. In such horizontal hole a helical spring 8| is inserted and such spring is engaged by a downwardly projecting pin 82 suitably secured to lever 14. Spring 6I therefore biases -lever 14 outwardly against the left side of the receiver.

Cover 9 is provided to close the top of receiver I in order to exclude dirt and other foreign matter as well as to support certain cams. Cover 9 is essentially a channel shaped member opening downwardly and, as previously men- The rear end of cover 9 is secured to back plate il by a conventional latch 84, the end of which engages a slot 85 provided in the back plate II, thus securing cover 9 in its closed position. To actuate the extractor 39, a cam 66 is secured in depending relation to the underside of cover 9 preferably by riveting. Cam 86 has an arcuatel A .feeding cam 88 is secured by riveting to the forward end of cover 9 on the underside thereof as shown in Fig. 2 to impart a sideways motion to lever 14. The detailed function of such cam will be described presently.

On the right hand side wall of the receiver I, a horizontal inwardly projecting cam rib |93 is provided which cooperates with arm 6| of cam bar lock 51. Inthe battery position of breech block 2, the cam rib |03 depresses arm 6I of cam bar lock 51 and hence raises lug 59 of cam bar lock 51 out of engagement with a notch |04 provided in the top of cam bar 69. However when breech block 2 is rearwardly of its battery position, cam rib |03 does not contact arm SI and hence cam bar lock 51 rotates, under the bias of spring 64, to a position where it can engage notch |04 in cam bar 60.

On the left side of the irearm as shown in Fig. 2, there is provided a ybracket 9| and mounted thereon is a belt holding pawl 89. Such pawl is mounted for limited pivotal movement on a longitudinal horizontal pin 90 supported by bracket 9|. A torsion spring 92 is mounted on the depending lug 8 of trunnion 5 to bias pawl 89 upwardly against the Side 0f receiver I- raul 89;

is of course mounted opposite the feedway 93 of receiver I.

On the opposite side of the firearm as shown in Fig. 2, there is mounted gas cylinder 94. Gas cylinder 94 is generally horizontally disposed and is secured to receiver I preferably by rwelding. Gas tube 21 communicates with the forward end of gas cylinder 94.

Operating rod 4 is essentially a comparatively short length of tubing, the forwardend of which terminates in a piston-like member 95.` A radial lug 96 is secured, preferably by Welding, to one side of operating rod 4 and oppositely disposed to such lug there is Welded an operating handle 91. The operating rod 4 is mounted alongside of receiver I in a tubular housing 99 with the piston end 95 cooperating with gas cylinder 94. Opposed longitudinal milling cuts are made on housing 99 thereby providing diametrically opposed slots |06 as shown .in Figs. 3 and y13 through which opposed lug 96 and operating handle 91 project so that operating rod 4 may readily telescope within housing 99. Lug 96 engages recess '66 of cam bar 60 when operating rod 4 is mounted on the side of receiver I.

A driving spring 98 when inserted in the hollow interior of operating rod 4 serves to drive operating rod 4 forwardly and, in turn, driving'the breech block 2 forwardly to the battery position as will be presently explained. The rear end of driving spring 98 is contained within housing 99. Such housing is supported at its rear end by a suitable bracket |09 secured to receiver I.

Operation To load the firearm shown in the accompanying figures, cover 9 is unlatched and raised to an upright position. The end of a belt of cartridges is fed transversely into feedway 93 of the firearm. Breech block 2 is first partially retracted then permitted to go forwardly whereupon the knifelike end 11 of lever 14 passes between the first and the next adjacent cartridge. Cover 9 is then lowered and secured to back plate I| Iby latch 84. To introduce a, vcartridge 46 into the chamber 41 of barrel 3, handle 91 on operating rod 4 is pulled rearwardly. Extractor 39 which is in engagement with the rim of a cartridge in the cartridge belt (not shown) withdraws the front cartridge rearwardly from the cartridge belt. The cartridge is then held against the back face of T-slot 18 until extractorv 39 strikes the arcuate surface 81 of cam 'B6 secured to the underside of cover 9. When such occurs, cam 86 forces extractor 39 downwardly and hence cartridge 46 in T-slot 18. Cartridge 46 is restrained from dropping out of thebottom Iof T-slot 18 by a suitable detent |02. As operating rod 4 is retracted, cam bar 60 and breech block 2 are likewise retracted, hence the cam bar lock 51 clears cam rib |03 and rotates into locking engagement with cam bar 66. y 1

When breech block 2- has been pulled back rearwardly until the rear face thereof strikes buffer plate I3 of the buffer mechanism I2, scar lug I1 will then engage sear notch 1| provided on the underside of breech block 2, hence holding such breech block rearwardly until release thereof is desired. Thus this firearm res from an open bolt position, that is, with the bolt held in the rearward position by the sear lug I1.` Belt holding pawl 89 retains the belt of cartridges within feedway 93 of the firearm when breech 1219er 2 here@ retracted V"1?? firs the firearm trigger l is pulled upwardly to disensase sear lug I'I from scar notch 1I. The bias of; driving spring 9 8 rapidly forces breech block 2 forwardly tothe battery position.

As the. breech block was moved rearwardly, belt feed lever I4 was withdrawn from the cartridge belt and also from engagement with feeding cam 88 and under the bias of spring 9i, belt feed lever i4 moves outwardly. Thus as the breech block starts forward, the forward end of the belt feed lever i4 passes between the first and second cartridges remaining in the belt. Thereafter the forward end of lever 7,4 engages feeding cam 88 andV is forced inwardly, thereby moving the belt of cartridges transversely into the gun, positioning the first cartridge in the b elt in alignment with the extractor 39.

Cam bar 60 remains locked to breech block 2 by cam bar lock 5l as breech yblock 2 goes forwardly into the battery position. When cam barA 60 is so locked to breech bleek l2, lug E55` of cam bar 6.9 is positioned to 'the rear of slot 31.

4When in such position, bar 6B must travel in the neighborhood of /S before it will strike the forward part of such slot. About the time, breech block 2 reaches battery position, arm 6I on cam bar lock 51 passes under cam rib IES. Such cam then forces arms 6I downwardly thereby disengaging lug 59 from notch IM on top of cam bar 60 thereby permitting such cam bar tc travel forwardly the EYB" distance permitted by slot 3l'. In effect, cam bar 60 over-travels breech block 2 as such breech block goes into battery position. Upon movement of cam bar 6l] relative to breech block 2, cam slot @S in cam bar Si] forces lock downwardly so that breech block 2 will be securely locked to receiver l prior to firing pin '61 on cam bar G striking the cartridge 'it in chamber 41 of barrel 3.

When cartridge 46 is discharged .by the blow from firing pin G'I, a portion of the bullet propulsion gases escapes through gas port 39, hence through gas regulator 3l and gas tube 2l to impinge upon the forward end of piston 95 of operating 1'od 4. Operating rod fi is thus driven rearwardly by such gases. As lug 9E on such operating rod rests within recess G6 of cam bar 60, such cam bar is likewise driven rearwardly.

The rearward movement of cam bar tu effects unlocking of lock 35. Unlocking of lock L35 however is not completed until cam bar Si] has travelled rearwardly approximately as mentioned before which provides ample dwell time -to inn C sure that the barrel pressure has dropped. to a safe value. Cam slot 63 in cam bar 69 raises lock 35 out of engagement with the bottom of receiver I. Cam bar lock 51 engages cam bar lili. Breech block 2 will be moved rapidly rearwardly by the i inertia energy of operating rod 4 plus som-e blowback force from the residual gas pressure in chamber IVI of the barrel.

As the head of the cartridge d6 in chamber IVI in engagement with T-slot 'I8 in the front face of breech block 2, such case is extracted from 8 in T-slot 'I8 to fall out ofthe bottom of 'lf-slot 18, thus making room for the next unflred cartridge and also disposing of the extracted cartridge case through a suitable opening in the bottom of 'receiver I.

When breech block 2 reaches the end of its recoil stroke, the remaining energy not absorbed by driving spring 98 is absorbed and dissipated by buffer mechanism I2, the rear face of breech block 2 striking the buifer plate i3 thereby transmitting the remaining energy to buffer mechanism I2.

The firearm shown in the appended drawings will nre continuously as long as trigger I5 is held upwardly by pressure of the finger. This keeps sear lug Il' out of engagement with sear notch TI thus permitting continuous automatic reuntil either the belt of ammunition contained in the gun is exhausted or until sear lug Ii is permitted to engage sear notch 1I.

If the rearm is lacking in power or appears to have too much power, the flow 0f gas impinging on the face of piston can be correspondingly increased or decreased as desired by rotating gas regulator 3i to properly align a larger or smaller port to admit a greater or lesser amount of gas through gas tube Z'I.

It is apparent therefore from the foregoing description that there is hereby provided a light machine gun of simplified construction which is capable of dependable sustained full automatic fire. it is also evident that there is here provided an automatic Weapon Iwhich is positively locked at the instant of discharge o f a cartridge and one that remains so locked until the breech pressure has been sufficiently lowered to permit safe unlocking of the breech member.

I claim:

l. in an automatic firearm, a receiver having an opening in the bottom thereof, a barrel fixedly securcd to said receiver, a bolt slidably mounted in said receiver for movement to and from battery position, a lock member vertically reciprocable in said bolt, a transverse pin fixedly secured in said lock member, a ring member mounted in said bolt for longitudinal movement to and from a cartridge-firing position, said firing member having an inclined cam slot arranged to engage said transverse pin in said lock member, and means for reciprocating said firing member when said bolt is in battery position whereby said transverse pin follows the inclination of said cam slot and thereby imparts vertical locking and unlocking movement to said bolt lock member into and out of engagement With said opening in said receiver.

2. In an automatic firearm, a receiver having an opening in the bottom thereof and a reinforced portion rearwardly adjacent said opening, abarrel fixedly secured to said receiver, a bolt slidably mounted in said receiver for movement Vto and from battery position, a cylindrical lock member vertically reciprocable in said bolt, said lock member having an` upwardly extending bifurcated portion, a pin member iixedly secured across said bifurcated portion, a firing member mounted in said bolt for limited longitudinal'movement'to and from a cartridge-firing position, said firing member having a forwardly projecting firing pin and a rectangular portion extending rearwardly through said bifurcated portion of said lock member, said rectangular portion having an inclined cam Aslot therein through which said pin member of said 'lock member extends, and a reciprocable operating member for'actuat'ing said firing 9 member whereby said inclined cam slot acts on said pin member to raise and lowerssaid lock member into and out of said opening in said receiver to lock and unlock said bolt when in battery position.

DOUGLAS V. SCHNEPEL.

REFERENCES CITED UNITED STATES PATENTS Name Date Lovelace May 18, 1909 Number Number 10 Number Name Date Hoagland et al Nov. 1, 1938 Birkgt May 7, 1940 BirkigiI Nov. 7, 1944 Moore Dec. 1 9, 1944 Schirokauer June 12, 1945 Green Aug. 6, 1946 FOREIGN PATENTS Country Date France Nov. 13, 1931 Great Britain Sept. 6, 1934 

